Feed device for a sewing machine

Abstract

A feed device has feed members for feeding a work, and a stepping motor for directly driving the feed members. The period of driving pulses for driving the stepping motor is determined by feed control means on the basis of a speed signal indicating an actual operating speed of the main motor of the sewing machine or on the basis of a selectively set speed. The feed control means controls the stepping motor so that the feed motion of the feed members is continued also after the completion of the thread tightening operation of the take-up lever in order that the needle thread is tightened properly by the feed motion of the feed members.

What is claimed is: 
     
       1. A feed device for a sewing machine including a needle, a main motor driving reciprocatively said needle, speed control means controlling the rotating pseed of said main motor, and feed means for feeding a work to be sewn; wherein said feed means comprises, a feed member engageable with said work,   a stepping motor driving said feed member directly to impart feed motion to said work,   signal generating means generating a feed signal corresponding to the magnitude of the feed stroke of said feed motion in phase with the reciprocation of said needle,   a detecting means for detecting a drive timing corresponding to a predetermined phase of said needle, and   feed control means responsive to said feed signal and a speed signal corresponding to the rotating speed of said main motor for controlling the period of command pulses to be supplied to said stepping motor so that said feed motion may be carried out between said drive timing and a given timing just before said needle contacts said work.   
     
     
       2. A feed device for a sewing machine according to claim 1, wherein said feed control means calculates the period of command pulses to be supplied to said stepping motor in accordance with said feed signal and said speed signal. 
     
     
       3. A feed device for a sewing machine according to claim 1, wherein said feed member comprises plural rollers operatively connected with said stepping motor. 
     
     
       4. A feed device for a sewing machine according to claim 1, wherein said feed control means is supplied with at least one speed signal every reciprocating cycle of said needle and controls the stop timing of said feed motion in accordance with said feed signal and said supplied speed signal. 
     
     
       5. A feed device for a sewing machine according to claim 1, wherein said feed control means is supplied with said speed signal corresponding to a desired speed set by a speed setting device. 
     
     
       6. A feed device for a sewing machine including a needle, a main motor driving reciprocatively said needle, a take-up member tightening the needle thread carried by said needle in phase with the reciprocation of said needle, speed control device controlling the rotating speed of said main motor, and feed means for feeding a work to be sewn; wherein said feed means comprises, a feed member engageable with said work,   a stepping motor driving said feed member directly to impart feed motion to said work,   signal generating means generating a feed signal corresponding to the magnitude of the feed stroke of said feed motion in phase with the reciprocation of said needle,   a detecting means for detecting a drive timing corresponding to a predetermined phase of said needle, and   feed control means controlling said stepping motor by calculating the period of command pulses to be supplied to said stepping motor in accordance with said feed signal and a speed signal corresponding to the rotating speed of said main motor for controlling the period of command pulses to be supplied to said stepping motor so that said feed motion may be carried out between said drive timing and a given timing just before said needle contacts said work.   
     
     
       7. A feed device according to claim 1, wherein said detecting means detects a timing signal corresponding to the uppermost position of said needle. 
     
     
       8. A feed device according to claim 1, including a take-up lever for tightening sewing thread in said needle and means for controlling said take-up lever to tighten said thread during a portion of said feed motion. 
     
     
       9. A feed device for a sewing machine including a needle, a main motor driving reciprocatively said needle, a take-up member tightening the needle thread carried by said needle in phase with the reciprocation of said needle, speed control means controlling the rotating speed of said main motor, and feed means for feeding a work to be sewn; wherein said feed means comprises, a feed member engageable with said work,   a stepping motor for driving said feed member directly to impart feed motion to said work,   a memory means for storing a feed signal representative of the magnitude of the feed stroke of said feed motion and for generating the feed signal in phase with the reciprocation of said needle,   a detecting means for detecting a drive timing corresponding to a predetermined phase of said needle,   a speed signal generating means for outputting a speed signal corresponding to the rotating speed of said main motor, and   a feed control means for calculating the period of command pulses on basis of said speed signal and said feed signal and for supplying said command pulses to said stepping motor, said feed control means being adapted to control the duration of supplying said command pulses so that said feed motion may be carried out between said drive timing and a given timing just before said needle contacts said work.   
     
     
       10. A feed device for a sewing machine according to claim 9, wherein said feed member comprises plural rollers operatively connected with said stepping motor. 
     
     
       11. A feed device for a sewing machine according to claim 9, wherein said feed control means is supplied with at least one speed signal every reciprocating cycle of said needle. 
     
     
       12. A feed device for a sewing machine according to claim 9, wherein said feed control means is supplied with said speed signal corresponding to a desired speed set by a speed setting device.